Limited Progress Cooling Fukushima's Nuclear Reactors

Units #5 and #6 Back to Normal TemperatureIt has now been about 10 days since a massive 9.0 earthquake and devastating tsunami hit Japan, damaging nuclear reactors at Fukushima I. Thankfully, there are signs of progress. While the most damaged reactors are still not under control, units #5 and #6 are now being cooled properly and efforts are still under way to restore proper water flow at the other reactors. Read on for some of the highlights of what happened over the past few days.

According to Kyodo News, the Japanese authorities said that the radiation levels found in water were "77 becquerels of iodine was found per kilogram of water in Tochigi, 2.5 becquerels in Gunma, 0.62 becquerels in Saitama, 0.79 becquerels in Chiba, 1.5 becquerels in Tokyo and 0.27 becquerels in Niigata, against an intake limit of 300 becquerels. The amount of cesium per kilogram of water was 1.6 becquerels in Tochigi and 0.22 in Gunma, against the limit of 200 becquerels set by the Nuclear Safety Commission of Japan." (What is a Bequerel?)

These numbers are low and don't pose health risks (the intake limit has a margin of safety built in - you don't get sick as soon as you reach 300 becquerels), and there's always some radiation present pretty much everywhere on the planet's surface, but it's good to keep monitoring the levels in food and water near the Fukushima plant just in case.

Saturday, Japanese troops in cooperation with the Tokyo Fire Department sprayed water on unit #3 until 01:10 JST.

Also on Saturday, electricity provided by emergency diesel generators allowed water pumps at units #5 and #6 to activated to help cool the spent fuel pools. This is good progress, but these were the least damaged units.

On Sunday, the restored emergency power to the spent fuel pond cooling systems for units 5 and 6 have "brought the unit 5 pond temperature down from 68.8 °C to 43.1 °C and the unit 6 pond temperature down from 67.5 °C to 52 °C as of 03:00 JST". Later that day, the water temperature dropped to 36.1 °C at Unit 5 and 36.6 °C at Unit 6.

On Monday, grey smoke was spotted coming out of the south-east corner of unit #3. TEPCO evacuated the site temporarily in case the smoke was radioactive. The smoke stopped after 6 PM JST.

White smoke, which was later thought to have been steam, was also spotted coming from unit #2, according to Kyodo News.

Also on Monday:

The government's Nuclear and Industrial Safety Agency said no injuries were confirmed in the incidents and that there have been no major changes in the radiation levels at the site. [...]

The government ordered Fukushima and three other prefectures Monday to stop shipping spinach and another leaf vegetable following the detection of radioactive substances in the produce at levels beyond legal limits, while trace amounts of radioactive substances were detected in tap water samples collected Sunday and Monday in nine prefectures. (source)

Photo: ASAHI SHIMBUN/STR/EPA/Corbis

Bill Borchardt, executive director for operations at the U.S. Nuclear Regulatory Commission, said that the containment domes at Japan's Fukushima Dai-Ichi nuclear reactors are intact and the situation at the plant "is on the verge of stabilizing," which is encouraging.